I’ve heard how space probes use their “sails” to make use of “solar winds” to travel distances. But isn’t space just vast emptiness with no resistance/ friction?
In: 4
Emptiness with block of matter and sometimes speeding waves of particles that will push you more gently than an asteroid.
Because essentially empty is not the same as totally empty. The two most relevant things to solar sails which pass through space are solar wind and light. Solar wind is a constant stream of charged particles released by the Sun’s atmosphere (wind from the sun, solar wind). These particles carry momentum and can therefore push objects. These particles are also responsible for things like Aurora.
The light emitted by the sun also carries momentum, when you have a sheet of something being hit by light it will feel a radiation pressure which pushes it in the direction the light is going.
Basically the Sun is big and powerful, so even though space is mostly empty you can take advantage of the momentum transfer from the Sun to you, and the fact there is very little resistance or friction means that those small forces can add up to large changes in position and velocity over a long time.
The solar wind is the stream of fast-moving charged particles that are produced in the sun’s atmosphere and “blow” outwards away from the sun. Solar wind doesn’t really “blow” spacecraft like real wind, but they can cause radiation damage, and indirectly alter the orbits of spacecraft in Earth orbit by causing the atmosphere to expand.
Solar sails use light pressure from photons, not the solar wind. Those are 2 different things. We don’t really have spacecraft that use solar sails except a few experimental ones. Light doesn’t have mass but it still has momentum, so if you have a large enough surface area, it can accelerate an object.
And yes, space is very empty, but it’s not completely empty. Even the most empty parts of space still contain some particles and some radiation.
The sun is not a lightbulb.
It’s a massive boiling sea of nuclear-powered hydrogen and helium in a constant state of explodium.
At any given time, that hydrogen is spraying off the sun in vast amounts and flying off into interstellar space.
By the time it gets out the 93 million miles to earth, it’s pretty tenuous and very low pressure. You wouldn’t notice it on your bare skin, A cloth sail wouldn’t noticeably ripple.
But for a very lightweight spacecraft with a large enough piece of foil as a sail, it’s a steady breeze outwards from the sun, and you can leverage that over long periods of time to get a fair amount of speed for free.
Latest Answers